When a release has changes that require special steps to migrate an existing orchard instance from the older version, these UpgradeFromXX modules are created to handle that. Typically it's for shuffling data around, or when a Part is eliminated or replaced
with another. For example, when the RoutePart was replaced with Autoroute (I think in 1.4), the UpgradeFromXX module replaced all RouteParts with corresponding AutorouteParts.

Thank you for your quick response. I think this is not mention in the documentation and it it's good to know that after every upgrade this module needs to be enabled so all upgrades are performed and then to be disabled, please correct me if I am wrong.